Automatic door closers are known. Generally they comprise a body portion adapted to be mounted to either a door post or the door and an arm mechanism adapted to be pivotally connected to the other of the door post and the door. When a door is opened, a spring system is loaded to store energy ready for closing the door when it is released. Usually, a damping mechanism is provided to control the speed of door closure. For example, the body portion may contain a chamber with a bleed screw and the arm mechanism connects to a piston within the chamber, the arrangement being such that closure operates against the resistance of air, the escape of which through the bleed screw permits the mechanism to close.
One example of a prior published door closer is that of Korean Specification No 97-7637 which proposes a cylindrical housing which receives a hinge shaft engaging with a piston element which is threadibly engaged on the hinge shaft and retained such that upon relative rotation the piston is driven down the cylindrical housing, thereby compressing a helical return spring. The housing has air chambers either side of the piston with a bleed valve arrangement to buffer return motion under the influence of the helical compression spring which has been compressed upon opening of the associated door.
Another prior proposal is that of International Patent Publication WO 99/54583 (Shin) which is a hinged type automatic door closer providing a cylindrical housing to be mounted on a door via a plate and accommodating a hinge shaft which is mounted on a door frame via a mounting plate. A helical threading is provided on the hinge shaft and engages with a guided piston which moves axially along the housing upon rotational movement corresponding to a door being opened. The helical compression spring below the piston is compressed. This door closer relies on a hydraulic damping system.
The prior art referred to has been published, but no admission is made that in any particular country, this art is generally known or used.
For many applications the present inventor considers that the prior art proposals have limitations and new and useful alternatives are needed to provide consumer choice with functionality and performance not hitherto available. Embodiments of the invention are especially applicable to installation such as swimming pool gates and preferred embodiments of the invention incorporate distinct and separate inventive concepts which can provide novel and useful simplified structures useful for various applications.